1H-pyrrole-[1,2-b][1,2,4]triazole derivatives are described, with respect to their reactivities, generally, in Ukrainski Khimicheskii Zhurnal, Vol. 41, No. 2, pages 181 to 185 (1975), and in Khimiya Geterotsiklicheskikh Scedine nii, No. 2, pages 261 to 267 (1974), and their use as medicines and the like is described in U.S. Pat. No. 4,358,457 and U.S. Pat. No. 4,962,202. Further, the derivatives are described as photographic magenta couplers and magenta dyes in Nihon Shashin Gakkai Showa 60-Nendo Nenji Taikai Koen Yoshi-shu, JP-A-62-278552 (“JP-A” means unexamined published Japanese patent application), JP-A-62-279339, JP-A-1-288835, U.S. Pat. No. 4,910,127 and EP-A-491 197.
Furthermore, U.S. Pat. Nos. 5,256,526, 5,384,236, and 5,547,826 disclose that 1H-pyrrole-[1,2-b][1,2,4]triazole derivatives can be made into compounds useful as photographic cyan couplers by introducing electron-attracting groups to the 6-position and the 7-position of the 1H-pyrrole-[1,2-b][1,2,4]triazole derivatives. As methods for synthesizing 1H-pyrrole-[1,2-b][1,2,4)triazole derivatives having electron-attracting groups at the 6-position and the 7-position, synthetic methods wherein 1H-1,2,4-triazole derivatives are used as a starting material are described in JP-A-5-202,004 and JP-A-5-255333. In addition, JP-A-7-48376 and JP-A-8-109172 disclose compounds useful as photographic cyan couplers and methods for synthesizing them, and also their efficient synthetic methods.
On the other hand, many general esterification methods that use condensation of carboxylic acids with alcohols are known, and examples are described in detail in Jikken Kagaku-koza, Vol. 22 (Maruzen, 1992), pp. 43 to 83. Among these, for example, a method for synthesizing an ester by using an equilibrium reaction in the presence of an acid catalyst under dehydration conditions, or a method for synthesizing an ester by using a condensing agent, such as dicyclohexylcarbodiimide and ethyl azodicarboxylate, are often used. Furthermore, there is an acid chloride method for synthesizing an ester, wherein a carboxylic acid is converted by means of thionyl chloride, phosphorus trichloride, or oxalyl chloride, to an acid chloride, and the acid chloride is subjected to addition reaction of an alcohol, in the presence of a base.
The foregoing general esterification methods, however, could not be applied to the synthesis of ester compounds represented by the below-shown formula (IX) using carboxylic acids represented by the below-shown formula (VII) and cyclohexanols represented by the below-shown formula (VI), which are intended to be condensed in the present invention. Namely, the method that uses acid catalysts is accompanied by the problem that large amounts of cyclohexanols are used, and the method that uses condensing agents and the acid chloride method can hardly give the intended ester compounds, because, in the esterification of cyclohexanols, carboxylic acid components are preferentially decomposed. Only one method, using trifluoroacetic anhydride ((CF3CO)2O), described in Journal of Organic Chemistry, Vol. 30, page 927 (1965), has been applied, but the reagent is expensive and the treatment of the waste liquid is complicated, making the method difficult for use as an industrial process.